Number of colors in screen print
When an artist is selling a screen print and it says it's a '9 color screen print' what does that mean exactly?
For example this: http://tragicsunshine.com/art_prints/mulholland-drive
24" x 36" 9 color Screen Print w/ Metallic Inks on 100 lb Cream Cover Paper. Edition of 300, signed and numbered.
Does that mean the artist literally only used 9 different colors to create that piece and then they're each layered on in the screen printing process? That seems pretty crazy that an artist would have to only choose from a handful of colors. I guess in the example I linked I can see just a few colors being used but the different shades, etc. make it seem like more.
Does that mean the artist literally only used 9 different colors to create that piece and then they're each layered on in the screen printing process?
That's exactly what it means! Screen printing is when the artist takes each pigment, and drags it across the image-imprinted screen, one at a time, layering the inks in a specific order to get their desired effect. 9 inks would actually make for a pretty high-quality screen print (as the sample image you posted certainly looks to be).
Here's an infographic from shopworks.com that shows the process for a 1-color screen print. Multiply that by 9 for a 9-color screen print. It's actually quite a bit of work!
One easy way to wrap your head around this is to think in terms of INKS not in terms of COLOURS. Having worked a lot in print, this has become second nature, but if you spend a lot of time working digitally then it won't be quite as simple.
The example you've given uses 9 different inks to create the design. That means that some areas will be screened over or under others with differing dot patterns to achieve certain shades. This is particularly obvious in the red inside of the banner shapes: the red is laid down with the navy blue laid over it as a shading tool.